Huge companies, yes. They'd still prefer to spend less money/resource/time if they have the option to though, hence why some large companies actively explore cross platform technology. Adobe did that with phonegap a long time ago.
You're talking about Electron there, which like phonegap is a browser wrapper and a different thing to RN. I don't believe RN is known to be a battery drain in general.
Badly, which is why we have a totally different approach in the form of RN, Flutter etc. The concept of cross platform support wasn't the problem, that's what we're chasing for a reason.
What are some well done cross platform apps that don't unnecessarily drain battery life? I can think of one - VSCode.